1. Field of the Invention
The present invention relates to an image formation apparatus and an image formation method.
2. Description of the Related Art
Generally, with image formation apparatuses which form images on recording sheets such as paper or the like, various detachable optional sheet supplying devices are detachably mounted to the image formation apparatus for supplying sheets to the image formation apparatus. Each of the various optional sheet supplying devices for specific image formation apparatuses may differ in the transportation speed at which the sheets are transported to the image formation apparatus, and the distance from the position where the sheets are loaded to the position where the sheets are received by the image formation apparatus, so in such cases the time from the image formation apparatus transmitting a command to the optional sheet supplying device to the effect that a sheet should be fed out and supplied to the image formation apparatus to the sheet reaching the position where the sheets are received by the image formation apparatus differs from case to case.
Accordingly, an arrangement has been employed wherein, in order to perform image formation corresponding to various types of optional sheet supplying devices with different time required for the sheets to reach the position of the image formation apparatus for receiving the sheets, the time required is stored in the optional sheet supplying device beforehand, and the image formation apparatus performs image formation actions corresponding to that optional sheet supplying device by making reference to this time required (e.g., Japanese Patent Laid-Open No. 7-117872).
However, with image formation actions using the conventional method, jamming detection and the like can be suitably performed corresponding to the mounting position of the optional sheet supplying device as to the image formation apparatus, but there are also some problems which the above-described required time alone cannot solve.
For example, the following problems may occur with electrophotography image formation apparatuses using the intermediate transfer method. Note that intermediate transfer is a method wherein multiple color toner images, each of a different color, are subjected to primary transfer from photosensitive drums onto an intermediate transfer belt where they are overlaid, and then the toner image made up of multiple colors is transferred all at once by secondary transfer onto a sheet which has been transported separately.
With electrophotographic image formation apparatuses using intermediate transfer, the amount of time from starting primary transfer, i.e., the time of the first color toner image being transferred onto the intermediate transfer belt, to starting secondary transfer of the image formed by the multiple color toner images which have been overlaid (hereafter referred to as “image formation time”), may be longer than the time necessary for the sheet to be picked up and transported to the secondary transfer portions (hereafter referred to as “sheet transport time”), depending on the optional sheet supplying device.
In such cases, a sheet upon which an image of a page is to be transferred is picked up from the optional sheet supplying device following starting the image formation of that page at the image formation apparatus, so at the point that there are no more sheets loaded on the optional sheet supplying device, image formation for the next page has already started, meaning that a toner image with no sheet to be transferred onto is formed on the intermediate transfer belt, necessitating cleaning processing and the like as well as adversely affecting the longevity of the photosensitive drum.
In order to solve such problems, it is desirable to have a configuration wherein the sheet supplying interval at which the optional sheet supplying device feeds sheets can be optionally switched over according to various conditions such as the number of remaining sheets, and wherein the image formation apparatus performs actions corresponding to the sheet supplying interval of the sheets being supplied from the optional sheet supplying device detachably mounted to the image formation apparatus.